linux/lib/genalloc.c
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   1/*
   2 * Basic general purpose allocator for managing special purpose memory
   3 * not managed by the regular kmalloc/kfree interface.
   4 * Uses for this includes on-device special memory, uncached memory
   5 * etc.
   6 *
   7 * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
   8 *
   9 * This source code is licensed under the GNU General Public License,
  10 * Version 2.  See the file COPYING for more details.
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/genalloc.h>
  15
  16
  17/**
  18 * gen_pool_create - create a new special memory pool
  19 * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
  20 * @nid: node id of the node the pool structure should be allocated on, or -1
  21 *
  22 * Create a new special memory pool that can be used to manage special purpose
  23 * memory not managed by the regular kmalloc/kfree interface.
  24 */
  25struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
  26{
  27        struct gen_pool *pool;
  28
  29        pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
  30        if (pool != NULL) {
  31                rwlock_init(&pool->lock);
  32                INIT_LIST_HEAD(&pool->chunks);
  33                pool->min_alloc_order = min_alloc_order;
  34        }
  35        return pool;
  36}
  37EXPORT_SYMBOL(gen_pool_create);
  38
  39/**
  40 * gen_pool_add - add a new chunk of special memory to the pool
  41 * @pool: pool to add new memory chunk to
  42 * @addr: starting address of memory chunk to add to pool
  43 * @size: size in bytes of the memory chunk to add to pool
  44 * @nid: node id of the node the chunk structure and bitmap should be
  45 *       allocated on, or -1
  46 *
  47 * Add a new chunk of special memory to the specified pool.
  48 */
  49int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
  50                 int nid)
  51{
  52        struct gen_pool_chunk *chunk;
  53        int nbits = size >> pool->min_alloc_order;
  54        int nbytes = sizeof(struct gen_pool_chunk) +
  55                                (nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
  56
  57        chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);
  58        if (unlikely(chunk == NULL))
  59                return -1;
  60
  61        spin_lock_init(&chunk->lock);
  62        chunk->start_addr = addr;
  63        chunk->end_addr = addr + size;
  64
  65        write_lock(&pool->lock);
  66        list_add(&chunk->next_chunk, &pool->chunks);
  67        write_unlock(&pool->lock);
  68
  69        return 0;
  70}
  71EXPORT_SYMBOL(gen_pool_add);
  72
  73/**
  74 * gen_pool_destroy - destroy a special memory pool
  75 * @pool: pool to destroy
  76 *
  77 * Destroy the specified special memory pool. Verifies that there are no
  78 * outstanding allocations.
  79 */
  80void gen_pool_destroy(struct gen_pool *pool)
  81{
  82        struct list_head *_chunk, *_next_chunk;
  83        struct gen_pool_chunk *chunk;
  84        int order = pool->min_alloc_order;
  85        int bit, end_bit;
  86
  87
  88        write_lock(&pool->lock);
  89        list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
  90                chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  91                list_del(&chunk->next_chunk);
  92
  93                end_bit = (chunk->end_addr - chunk->start_addr) >> order;
  94                bit = find_next_bit(chunk->bits, end_bit, 0);
  95                BUG_ON(bit < end_bit);
  96
  97                kfree(chunk);
  98        }
  99        kfree(pool);
 100        return;
 101}
 102EXPORT_SYMBOL(gen_pool_destroy);
 103
 104/**
 105 * gen_pool_alloc - allocate special memory from the pool
 106 * @pool: pool to allocate from
 107 * @size: number of bytes to allocate from the pool
 108 *
 109 * Allocate the requested number of bytes from the specified pool.
 110 * Uses a first-fit algorithm.
 111 */
 112unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 113{
 114        struct list_head *_chunk;
 115        struct gen_pool_chunk *chunk;
 116        unsigned long addr, flags;
 117        int order = pool->min_alloc_order;
 118        int nbits, bit, start_bit, end_bit;
 119
 120        if (size == 0)
 121                return 0;
 122
 123        nbits = (size + (1UL << order) - 1) >> order;
 124
 125        read_lock(&pool->lock);
 126        list_for_each(_chunk, &pool->chunks) {
 127                chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 128
 129                end_bit = (chunk->end_addr - chunk->start_addr) >> order;
 130                end_bit -= nbits + 1;
 131
 132                spin_lock_irqsave(&chunk->lock, flags);
 133                bit = -1;
 134                while (bit + 1 < end_bit) {
 135                        bit = find_next_zero_bit(chunk->bits, end_bit, bit + 1);
 136                        if (bit >= end_bit)
 137                                break;
 138
 139                        start_bit = bit;
 140                        if (nbits > 1) {
 141                                bit = find_next_bit(chunk->bits, bit + nbits,
 142                                                        bit + 1);
 143                                if (bit - start_bit < nbits)
 144                                        continue;
 145                        }
 146
 147                        addr = chunk->start_addr +
 148                                            ((unsigned long)start_bit << order);
 149                        while (nbits--)
 150                                __set_bit(start_bit++, chunk->bits);
 151                        spin_unlock_irqrestore(&chunk->lock, flags);
 152                        read_unlock(&pool->lock);
 153                        return addr;
 154                }
 155                spin_unlock_irqrestore(&chunk->lock, flags);
 156        }
 157        read_unlock(&pool->lock);
 158        return 0;
 159}
 160EXPORT_SYMBOL(gen_pool_alloc);
 161
 162/**
 163 * gen_pool_free - free allocated special memory back to the pool
 164 * @pool: pool to free to
 165 * @addr: starting address of memory to free back to pool
 166 * @size: size in bytes of memory to free
 167 *
 168 * Free previously allocated special memory back to the specified pool.
 169 */
 170void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
 171{
 172        struct list_head *_chunk;
 173        struct gen_pool_chunk *chunk;
 174        unsigned long flags;
 175        int order = pool->min_alloc_order;
 176        int bit, nbits;
 177
 178        nbits = (size + (1UL << order) - 1) >> order;
 179
 180        read_lock(&pool->lock);
 181        list_for_each(_chunk, &pool->chunks) {
 182                chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 183
 184                if (addr >= chunk->start_addr && addr < chunk->end_addr) {
 185                        BUG_ON(addr + size > chunk->end_addr);
 186                        spin_lock_irqsave(&chunk->lock, flags);
 187                        bit = (addr - chunk->start_addr) >> order;
 188                        while (nbits--)
 189                                __clear_bit(bit++, chunk->bits);
 190                        spin_unlock_irqrestore(&chunk->lock, flags);
 191                        break;
 192                }
 193        }
 194        BUG_ON(nbits > 0);
 195        read_unlock(&pool->lock);
 196}
 197EXPORT_SYMBOL(gen_pool_free);
 198
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